Analysis of the yield curves and the angular distributions of the reactions F 19 (p, α 0) O 16 and F 19 (p, α π) O 16∗

Abstract

By analysis of the angular distributions of α-particles from the reactions F 19 (p, α) O 16 leading to the ground state and first excited state of O 16 (α 0 and α π respectively), virtual levels of the nucleus Ne 20 with spin and parity (even) + and (odd) − were investigated. Legendre polynomial expansions were adjusted to the data and the coefficients determined over the energy interval from 650 keV to 1500 keV. These results were then interpreted in terms of the resonance parameters of the compound levels presumed, and the following J-values were assigned: J = 2 levels at 731, 778, 843, 1115 and 1356 keV, a J = 1 level at 1250 keV and a J = 0 level at 1160 keV. Background yields are probably due to a few broad levels of J = 0 and 1. For the α 0-channel, vector diagrams of five elements of the collision matrix concerned, which correspond to two values of entrance channel spin and three values of relative orbital angular momentum, were drawn, which reproduce almost all details of observed excitation functions. This procedure gives information about the relative signs of the reduced width amplitudes of the virtual levels. This sign seems to be independent of the entrance channel spin in spite of large fluctuations of the relative yield in both channels from level to level. Yields of α 0, α π and protons from each resonance are compared and the reduced widths of levels of Ne 20 are estimated.